This invention generally relates to the formation of containers of thermoplastic material fron an extruded tube of thermoplastic material. More particularly, this invention relates to formation of such containers utilizing a preliminary or preform shape which is made directly from the extruded tube of material. Specifically, this invention relates to a method of making a thermoplastic container having a memory in a collapsed or folded state by deformation of a preform shape while the interior of the walls of the preform shape are still in a deformable state.
The manufacture of blown thermoplastic containers using an intermediate preform shape is known in the art and is illustrated in U.S. Pat. Nos. 3,767,747 and 3,781,395. In addition, thermoplastic containers designed to facilitate the dispensing of their contents are also known. Examples of such containers may be seen in U.S. Pat. Nos. 3,301,293, 3,319,540 and 3,819,789. However, one flaw in these prior art containers is that during forming their material received a memory of their final shape. Thus, when dispensing the contents of these containers, the container returns to its original as formed shape whenever external pressure applied to dispense the contents is released. This is undesirable because it makes complete dispensing of the contents of such containers somewhat difficult. Good examples of this situation are thermoplastic tubes for shampoo or toothpaste. These tubes always try to return to their original, tubular shape after being squeezed. U.S. Pat. No. 3,301,293 shows one example of a structure to overcome this problem. However, the solution is purely mechanical and the locking features of the container adds undesirable complexity to the molding or forming process. I have found that these deficiencies in the prior art can be overcome by molding in a memory of the collapsed state in a thermoplastic container. As the contents of such a container are dispensed, the memory tends to urge the container toward a collapsed state, thereby leading to more efficient and easier dispensing of the entire volume of product in such a container.